Such a knife is known from public prior use. It has a housing with a blade holder in which a knife blade is held. The blade holder has a main part and a holding part. The blade is held between a surface of the main part and a surface of the holding part in a blade seat. The holding part is movable between a holding position and a blade replacement position. In the blade holding position the blade is held tightly in the blade seat between the holding part and the main part. In the blade replacement position the holding part is spaced or pivoted away at least partially from the main part, so that the blade can be removed from the blade seat and a new blade can be inserted into the blade seat.
The housing has two housing parts. A housing body is movable relative to a housing insert between a closed position and an open position. The housing body is part of an actuating system. The holding part is moved from the blade holding position into the blade replacement position by movement of the housing body from the closed position into the open position.